1. Field of the Invention
The present invention relates to an apparatus for displaying an operation sequence of a numerically controlled machine tool, wherein successive operations of the numerically controlled machine tool commanded by a machine operator are memorized during an operation and are displayed for malfunction analysis when the numerically controlled machine tool is stopped due to malfunction.
2. Discussion of the Prior Art
Heretofore, a numerical controller has been known which controls a machine tool in accordance with a numerical control program which is created based upon machining data input through a data input device. The prior numerical controller is provided with a function of displaying on a cathode-ray tube monitor information for monitoring the status of the machine tool. The monitor information is composed of a block number of a numerical control program which is being executed, a commanded moving amount of a movable element of the machine tool, the present position of the movable element, and the remainder of the commanded moving amount and the like. The displayed monitor information is updated when the numerical control program is executed in the automatic operation mode, or the manual feed handle for generating manual feed pulses is rotated by a machine operator in the manual operation mode. In the event that the machine tool stops because of a malfunction, the machine operator can know the status of the machine tool based upon the displayed information.
Since the displayed information just indicates the present status of the machine too, and such information disappears if the operation of the machine tool is continued after the occurrence of the malfunction, it is difficult to analyze the cause of the malfunction based upon the displayed information.
To analyze the cause of a malfunction, it is required to know the operation sequence of the machine tool, i.e., successive operations which the machine operator instructed the numerical controller before the occurrence of the malfunction, as well as the monitor information as described above. The prior numerical controller, however, just monitors the execution of the numerical control program as explained above, but does not memorize the operation sequence. The machine operator therefore has to remember the successive operations to analyze the cause of the malfunction. Since it is difficult for the machine operator to precisely memorize the operation sequence, the malfunction analysis based on the operator's memory is inefficient. Further, it is difficult to revive the malfunction, because the operation sequence is not memorized accurately.